Process of producing photo-electric cells



v T. w. CASE. PROCESS OF PRODUCING PHOTO-ELECTRIC CELLS.

APPLICATION FILED AUG.27. 1920- 6ource q Alternating Current ATTOBIV 1 8Patented May 3, 1921.

UNITED STATES THEODORE W. CASE, OE SCIPIO, NEW YORK.

PROCESS OF PRODUCING PHOTO-ELEGTRTC CELLS.

Specification of Letters Patent.

Patented May 3, 1921.

Application filed August 27, 1920. Serial No. 406,462.

To all whom it may concern:

Be it known that I, THEODORE W. CASE, of Scipio, in the county ofCayuga, in the State of'New York, have invented new and usefulImprovements in Processes of Producing Photo-Electric Cells, of whichthe following, taken in connection with the accompanying drawings, is afull, clear, and exact description.

This invention relates to certain improvements in processes ofmanufacturing photoelectric cells.

The obje'ct of the invention is to produce a highly efiicient cell ofthe character described, and which shall be of simple con-- 'struction,unusually constant and uniform in reaction and relatively permanent inits activity.

Other objects and advantages relate to the details of the processinvolving certain preferred, but perhaps non-essential steps, all ofwhich will more fully appear from the following description taken inconnection with the accompanying drawings, in which Figure 1 is adiagrammatic view illustrating a method of carrying out one step of theprocess.

Fig. 2 is a diagrammatic view illustrating a manner of use of thephoto-electric cell as roduced by this invention. I he process comprisesprimarily the coating of an electrode capable of being heated, such as afilament with a suitable material, as, for instance, metallic oxid suchas strontium oxid, barium oxid or calcium oxid. This coating may beproduced upon the filament in any suitable way as by dipping the same instrontium nitrate, barium nitrate or calcium nitrate, respectively, at asuitable temperature to cause the same to flow upon the filament, andthereby changing the nitrates of the elements to the oxids.

The coated filament is then placed in an ordinary glass tube or bulbopposite a metallic electrode as for instance a nickel plate. The bulbis then evacuated and the whole is baked at such a temperature as may besuitable for eliminating practically all traces of gases. Then theheated filament and metallic electrode are connected incircuit with asource of sufficiently high potential so as to heat the plate red hot,thus driving off from the metallic electrode any remainin traces ofgases and oxygen. Y

The metallic electrode temperature is then the high potential existingbetween the 'electrodes acts as a directive agency and causes thethrown-off material to deposit upon theplate in a thin layer where it iscontinuously bombarded by the cathode rays or electrons emanating fromthe heated filament.

' It is believed that when the filament, as described, is coated with ametallic oxid such as barium oxid, that the oxid is lost when thematerial is thrown off from the filament and that the deposit upon themetallic electrode is substantially pure metal, as for instance, barium.strontium. calcium.

or a compound of sodium and potassium,

dependent upon the character of the coating. \Vhether the reduction isdue to the bombardment of electrons or not is not known.

Although a high potentialdirect current is suitable for the purposedescribed. the applicant in his work has usually incorporated atransformer in the circuit whereby the potential of the alternatingcurrent available was stepped up to an extent suitable for mosteffectively acting as a directive agency of the material thrown off fromthe heated filament. During this step of the operation the'tube or bulbis connected to a suitable vacuum pump for maintaining a substantiallycomplete vacuum within the bulb.

The deposition may be maintained for stated intervals, as, for instance,five minute periods, and after each such period the photoelectricqualities of the cell may be tested in comparison with a constant sourceof light, and when the maximum re-action .is obtained, or the actiondesired, the vacuum pump may be shut off and the tube containin thefilament and metallic electrode sealed. uring'the process ofmanufacture, when using a direct current, the potential in the circuitis so arranged as to maintain a positive potential upon the metallicelectrode and a negative potential upon the filament.

In Fig. l I have diagrammatically illustrated a hookup suitable forcarrying out the depositing step of this process in which the filament-l is connected in an independent heating circuit -2 with a source ofpotential 3 and in which the circuit between the filament 1 and metallicelectrode 2 includes the secondary 4 of a transformer, the primary ---8of which is connected in circuit with a suitable source 9- ofalternating current. The secondary of the transformer embodies aconsiderably larger number ofcoils than the primary to produce desiredvoltage. When the process of producing the cell is completed, asdescribed, the filament is thereafter used. as an unheated electrode,and any other form of electrode may be substituted.

In Fig. 3 I have illustrated the cell in a hook-up suitable formeasuring light intensity in which two electrodes are connected incircuit with a source of potential 7- and a galvanometer 5-. Variationsin .the light rays to which-the cell (which includes the electrodes -1and 2 and the vacuum tube or bulb 6) is exposed two or more materials(such asbarium oxid and strontium oxid) desired to form the sensitiveelement of the cell, and by carrying out the method as' hereindescribed, the two or more coatings will be thrown off from the,filament and will deposit upon the metallic electrode and constitute aunitary coating thereon.

All traces of oxygen should preferably be removed from the bulb 6 but'itmay be desirable at times, and my invention permits of introducing intothe bulb ''1-6- a quantity of an inertgas such as Argon or Helium.

-Under such circumstances it may be suggested that the photo electronsemitted by the action of light ionize the inert gas by compact resultingin maximum conductivity.

The physical structure of the metal so deposited is not at present knownwith absolute certainty, and the theory of the action that results inthe unexpected sensitivity of the element so produced is more or less amatter for intelligent speculation, and the applicant hesitates to statepositively any definite theory and desires to confine himin obtainingthe desired spectral sensitivity of the cell by combining the propersubstances on the filament to be deposited on the metallic electrode,and by permitting control of the deposition by proper potential. betweenthe electrodes and proper temperature.

Although I have described a particular process embodying specificdetails as illustrative ofa method of producing the perhaps preferredproduct, yet many of the preferred details and some of the stepsdescribed as useful in producing such a preferred product may beomitted, or substitutions may be made therefor without departing fromthe invention as set forth in the appended claims.

l. The process of producing a photo-electric cell comprising coating aheatable electrode with suitable material, inclosing said electrode anda second electrode in a vessel under vacuum, heating said electrode tothrow off said coating connecting said electrodes in an electricalcircuit, whereby the said thrown-oil material deposits on the secondelectrode under bombardment of electrons.

2. The process of producing a photo-electric cell comprising coating afilamentary electrode with suitable material, inclosing said electrodeand a second electrode in a vessel under vacuum, heating said electrodeto throw olf said coating connecting said electrodes in an electricalcircuit, whereby the said thrown-01f material deposits on the secondelectrode under bombardment of electrons.

electrodes as it is thrown ofl' from the other electrode.

4. The process of producing a photoelectric cell comprising'depo'sitinga coating of light, re-active material u on one of the electrodes'as itis thrown off rom the other electrode by the action of heat.

5. The process of producing a photo-electric cell'comprising depositinga coating of l ght, re-actlve material upon one of the elec trodes as itis thrown off from the other electrode, and subjecting such material asdeposited to bombardment by cathode rays.

6. The process of producing a photo-electric cell comprising depositinga coating of light, re-active material upon one of the electrodes as itis thrown ofi from the other electrode by the action of heat andsubjecting such material as deposited to bombardment by cathode rays.

7. The process of producing a light reactive electrode, comprisingcoating an electrode with suitable material, inclosing said electrodeand a second electrode in a vessel under vacuum,.heating said electrodehaving the light reactive coating to throw off said coating, connectingsaid electrodes in an electrical circuit, whereby the said thrown-offmaterial is directively deposited in a layer on the second electrodeunder electron bombardment.

8. The process of producing an electrode embodying a layer of lightreactive material, consisting in inclosing two electrodes in a vacuumvessel, one of which electrodes comprises a material desired to form thelayer upon the other electrode, connecting said electrodes in a circuit,including a source of potential, heating the said electrode whichcomprises the material desired to form the layer to disintegrate thesaid material and cause it to be thrown off, and directively depositedin the form of fine particles upon the other electrode under electronbombardment.

9. The process of producing an electron emitting cathode comprisingdepositing a layer of suitable material upon an element constituting aportion of said cathode, while the said element is operatively connectedin circuit, as an anode, with another electrode,

which comprises the material to be deposited.

10. The process of producing an electron emitting cathode comprisingcoating a heatable electrode with suitable material, inclosing saidelectrode and a second electrode in a vessel under vacuum, heating thesaid heatable electrode to throw off the said coating, connecting saidelectrodes in an electrical circuit whereby the said thrown-ofi'material deposits on the second electrode in the form of fine particlesand under bombardment of electrons.

In witness whereof I have hereunto set my hand.

THEODORE w. CASE.

Witnesses:

CARL J. SPONABLE, JOHN TABER.

